Adapting to Storms and Flooding

Increased frequency of storms and severity of flooding prompts beach community to look for solutions.

Localized flooding has been an ongoing occurrence in the seaside town of Old Orchard Beach, Maine. Increased frequency and severity of flooding prompted the Town to hire Wright-Pierce to investigate causes and potential solutions. Wright-Pierce assisted the Town with a study and design of flood adaptation measures along West Grand Avenue, an emergency evacuation route for the town.

The West Grand Avenue storm water conveyance network consists of saltwater marshes, freshwater marshes, natural channels, road culverts, subsurface piping, and a tide gate. During the study phase of the project, Wright-Pierce determined that flooding was attributable to both watershed runoff and tidal influences. The most severe flooding occurred when the peak runoff rates occurred during a high tide. An analysis of the existing marsh storage capacity revealed that during high tide, a significant portion of the marsh volume was filled with saltwater. Runoff from large storms during high tide could not be stored within the already filled marsh, resulting in localized flooding of private residences and emergency evacuation route roadways.

The Town is currently engaged with environmental interest groups, most notably, the Sea Level Adaptation Working Group (SLAWG). Wright- Pierce coordinated with the SLAWG throughout the design process, and considered sea level rise when developing adaptation strategies. Wright-Pierce recommended and designed several local improvement projects in the problem area, including modifications to tide gate controls and operations, local stormwater infrastructure improvement, marsh invasive plant removal, and a flood control berm.